1. Field of the Invention
The present invention relates to a liquid processing system for performing a predetermined liquid process, such as a cleaning process, on a substrate, such as a semiconductor wafer.
2. Description of the Related Art
In the process of manufacturing semiconductor devices or flat panel display devices (FPD), liquid processes are frequently used, in which a process liquid is supplied onto a target substrate, such as a semiconductor wafer or glass substrate. For example, processes of this kind encompass a cleaning process for removing particles and/or contaminants deposited on a substrate, and a coating process for applying a photo-resist liquid or development liquid in a photolithography stage.
As a liquid processing system used for this purpose, there is a system comprising a plurality of processing units of the single-substrate processing type and a transfer unit for transferring substrates to and from the processing units. Each of the processing units is structured such that a substrate, such as a semiconductor wafer, is held on a spin chuck, and a process liquid is supplied onto the front surface or front and back surfaces of the wafer, while the wafer is rotated. In order to realize a high throughput while suppressing an increase in the footprint of a system, an arrangement frequently used comprises processing units stacked one on the other to form a multi-layer structure (for example, Jpn. Pat. Appln. KOKAI Publication No. 2005-93769).
In a liquid processing system of this kind, process liquid supply units for supplying process liquids (chemical solutions) are disposed for the respective process liquids to circulate and supply the respective process liquids. However, where a plurality of processing units are stacked one on the other, the piping layout for circulating and supplying process liquids inevitably brings about up-and-down portions of pipes. Consequently, the piping layout becomes complicate and occupies a large space. Further, the distances from processing units to the collective exhaust/drain system differ from each other between processing units, which may make it difficult to perform a uniform process between the processing units.